Case Study 11

GOOD PRACTICE CASE STUDY

11

COMPRESSED AIR CASE STUDIES

Compressed air at Wyeth Medica, Newbridge, Co.Kildare.

Compressed air is widely used in all aspects of industry. It is nonhazardous, readily available, can be stored easily and is a convenient source of power for a range of machines and tools. However, it is not cheap to operate. Approximately 10% of all electrical power in industry is employed in compressing air. Over its lifetime the operating cost of a compressed air plant will be many times its initial purchase and ongoing maintenance costs. Typically, the life cycle costs of a compressed air system can be broken down in Table 1 as follows:TABLE 1. SUMMARY OF LIFE-CYCLE COSTS

CAPITAL 18%

MAINTENANCE 5%

ENERGY 77%

Typical on-site savings have been estimated to be up to 30% of the energy input to the compressor. These savings are achievable through initially selecting the most efficient type of compressor, ensuring the correct air system design and ongoing efficient operation and good maintenance. It includes maximising the use of the latest technologies available and also ensuring that attention is paid to the simple measures of good housekeeping and primarily, keeping leakage rates to a minimum. The Annual Self Audit and Statement of Energy Accounts Scheme is operated by the Irish Energy Centre for the largest energy consumers in the industrial sector in Ireland. Participation in the scheme is voluntary with member companies committing to annual energy savings targets, regular audits of their energy consumption, and the publication of an annual statement of their achievements. The Irish Energy Centre provides support to the membership by helping in the preparation of annual statements and also through workshops, seminars, newsletters and site visits, and by providing information on specific approaches to energy efficiency.

IRISH ENERGY CENTRE www.irish-energy.ie

As part of the scheme, the Irish Energy Centre contracted Air Technology Ltd., U.K. to conduct comprehensive energy audits of the compressed air facilities at Carbery Milk Products, Ballineen, Co. Cork and at Wyeth Medica, Newbridge, Co. Kildare.

TABLE 2. SUMMARY OF AUDIT COSTS AND SAVINGS IDENTIFIED SITE

CARBERY MILK PRODUCTS

ANNUAL COMPRESSED AIR COST

€102,000

€203,000

COST OF AUDIT

€17,000

€25,000

POSSIBLE ANNUAL SAVINGS IDENTIFIED

€42,200

€99,600

41%

49%

SAVINGS AS A PERCENTAGE OF TOTAL COSTS

WYETH MEDICA

GOOD PRATICE CASE STUDY Compressed Air

THE AUDIT The audits were measurement based and covered all areas of the air systems. The aim of the audits was to identify economies in the rational use of compressed air through the on-site measurement of compressor efficiency, air demand pattern and air quality. The audits also made recommendations for improving system efficiency and outlined a strategy for reducing overall compressed air costs.

TABLE 3. DETAILS OF CARBERY COMPRESSED AIR SYSTEMS SYSTEM

COMPRESSOR

TREATMENT SYSTEM

SUPPLY PRESSURE

DISTRIBUTION (ALL SPUR SYSTEMS)

MAIN FACTORY

2 OFF 263 CFM OIL FREE SCREW

REFRIGERANT DRYER PLUS 3 STAGE FILTRATION

6-6.5 BARG

100 MM Ø REDUCING TO 50 MM Ø AND LESS AND FURTHER TO 10 MM Ø NYLON TUBING

1 OFF 269 CFM OIL FREE SCREW 1 OFF 202 CFM OIL FREE PISTON

The audits were carried out over the course of a week with little or no disruption to the operation of the individual sites.

ALCOHOL PLANT

2 OFF 430 CFM OIL INJECTED SCREW (VARIABLE SPEED DRIVE)

3 STAGES FILTRATION REFRIGERANT DRYER (TO BE INSTALLED)

6 BARG

100 MM Ø TO MANIFOLD WHICH FEEDS FERMENTERS. 50 MM Ø FOR GENERAL PURPOSE AIR

On both sites, rotary screw compressor efficiency was tested to ISO 1217 Annex C, which assesses the compressor in terms of its output and its power consumption; and centrifugal compressor efficiency was tested to ASME PTC10. The test results showed that it is essential that compressors are correctly maintained if they are to operate at their designed output and performance level. Regular monitoring of compressor operation will help to alert maintenance staff when performance is below standard.

CHEESE PLANT

1 OFF 202 CFM OIL FREE PISTON

REFRIGERANT DRYER PLUS 3 STAGE FILTRATION

9 BARG

50 MM Ø REDUCED AT TAKEOFF AND POINT OF USE

DIGESTER PLANT

1 OFF 75 CFM VANE

REFRIGERANT DRYER PLUS 2 STAGE FILTRATION

7 BARG

25 MM Ø

with a comprehensive site monitoring system connected to a number of electricity meters and also various flow and other meters.

» €1060 a year could be saved by shutting down the alcohol plant compressors overnight, when all the fermenters are not in use.

Measurement of Air Demand & Quality

» There was a problem with pressure drop in the cheese area when the cheese cutters were operating. This could be improved by re-piping the air booster arrangement to feed the accumulator before supplying the process.

The air delivered from each compressor station was measured over a period of a week, including isolation of specific plant to investigate leakage rates. The air quality delivered by each system was also measured. Evaluations of the results of these measurements led to the following conclusions:

Compressors at Carbery Milk Products.

CARBERY MILK PRODUCTS LTD., BALLINEEN, CO. CORK Carbery Milk Products was established in 1965, and since then has evolved into a leading international food company producing a successful range of food ingredients and cheese and ethanol products. Compressed air is an essential part of the production process at Carbery. It is used for a variety of process and instrument applications. The annual cost of generating compressed air for the plant was calculated to be €102,000.

» The large amount of small bore nylon pipe used in the plant was contributing to the plant’s pressure drop problems. Long lengths of narrow bore nylon tubing should be replaced with steel pipe work. » The night/non-production time demand was quite high, indicating a high leakage rate or misuse of air.

Compressed air is generated at four separate locations at the plant, each location supplying individual systems. These consist of a main factory system and 3 satellite systems, namely the alcohol plant, the cheese plant and the digester plant. All systems are linked for backup purposes, although the links are usually closed. A summary of the systems, their compressors, and treatment systems is presented in Table 3 above. The site suffers from problems due to low air pressure during spring and summer time when milk production is high. Management is active in trying to reduce energy consumption Carbery Milk Products, Balineen, Co. Cork.

» Air efficient nozzles should be fitted on the labelling machines in the cheese plant. » Solenoid valves should be used throughout the plant to switch off the air supply when a machine is not in use. » €4,000 per year could be saved by linking the alcohol plant and the main factory compressed air systems. » €3,100 to €5,740 per year could be saved by linking the main factory and digester compressor. » €4,000 per year could be saved by supplying most of the cheese plant system from the factory air.

GOOD PRATICE CASE STUDY Compressed Air

System Leakage A comprehensive leakage survey using ultrasonic leak detection equipment was carried out as part of the audit and a total of 78 leaks were identified. Fifty of these leaks were medium to very large in size. It was determined that carrying out a comprehensive leak reduction programme as part of a planned maintenance system could achieve an annual saving of €28,400.

Recommendations The audit identified a total savings potential of close to €42,200 for the Carbery Milk Products site. The main recommendations for savings lie in reducing leakage, which is currently very high, and linking the compressed air systems. 19 other recommendations were also made for individual plant areas covering items such as flow meter recalibration, upgrading nylon airlines, installing automatic drains and air efficient nozzles at the end users. Wyeth Medica Ireland Ltd., Newbridge, Co. Kildare

WYETH MEDICA IRELAND LTD., NEWBRIDGE, CO. KILDARE Compressed air is generated in a central compressor house by 4 oil free compressors, which supply the tablet manufacturing, packaging and warehouse areas. The installed compressors are two Ingersoll Rand CV35MX2 two stage, oil free centrifugal compressors and two Atlas Copco ZR145 two stage, oil free rotary screw compressors. Process and instrumentation air is treated by a desiccant dryer, while the breathing air is treated by a refrigeration dryer. Following treatment, the air is distributed to the main processing area. Details of the generation, treatment and distribution system are presented below in Table 4. The rapid expansion of the plant over the last few years has led to problems of low air pressure in certain areas during peak demand periods.

Measurement of Air Demand & Quality The air demand delivered upstream of the dryers was measured over a period of a week. The demand profiles indicated a varying requirement throughout the day, typically starting with a low requirement between midnight and 8am, before rising to the higher demand throughout the remainder of the day.

per annum and would enable demand to be met by one centrifugal compressor and one screw compressor. The use of pressure regulators, with a continuous loss, in the tablet manufacturing area is one of the major causes of leakage at the plant. If these leaking regulators were replaced, both dryer purge losses and centrifugal compressor hours of operation would be reduced.

Recommendations The audit found a lot of good practice in evidence at Wyeth Medica but also identified areas of potential savings. A total savings potential of about €94,000 per year was identified, but this would require some investment in order to be realized. Recommendations for the site arising from the audit were as follows: » The screw compressors usually operate at a bandwidth of 0.6 bar. The installation of a control system that operates with a mean pressure of 7.7 bar and that maintains a narrower bandwidth of 0.3 bar across both screw compressors would save €760. Note: On many sites this setting is often 1 bar or more, thereby increasing running costs particularly at times of low demand.

» The tests on the centrifugal compressors show that they are operating in a throttled condition due to the setting of the high current limit switch. If this setting was adjusted so that the compressors could operate at maximum output, the demand on the screw compressors would be reduced and there would be a resulting saving of €2,244 per annum. » The installation of autodrains in the compressor house would reduce purge losses by an estimated 25 Scfm and save €2,310 per annum. » A programme to continuously monitor and repair leaks would save energy by reducing air consumption, dryer purge loss and hours of operation of the screw compressor. This would results in savings in the region of €22,440 per annum. » A problem with pressure drop in the packaging area, could be solved by upgrading the small diameter nylon tubing to at least 10mm diameter pipe. This would also allow a 0.5 bar reduction in compressor generation pressure, thereby reducing power consumption, increasing the output duty centrifugal compressor and reducing demand due to lower leakage rates. This would result in savings of between €5,280 and €11,220 per annum. » The use of air efficient nozzles that are properly regulated and isolated when they are not required would help to reduce energy costs. » The replacement of relieving regulators with the non-relieving type could result in savings of up to €60,700.

TABLE 4. DETAILS OF COMPRESSOR AIR SYSTEMS

System Leakage A comprehensive leakage survey using ultrasonic leak detection equipment was carried out as part of the audit and a total of 128 leaks were identified. Thirty-five of these leaks were medium to very large in size and hence required immediate attention. Repairing these leaks would save €22,400

COMPRESSOR

TREATMENT SYSTEM

SUPPLY PRESSURE

DISTRIBUTION

2 OFF 1,270 CFM OIL FREE CENTRIFUGAL

REFRIGERANT DRYER

7.9 BARG

67 MM Ø BREATHING AIR 108 MM Ø UNDERGROUND TABLET & PACKAGING

2 OFF 697 CFM OIL FREE SCREW

DESICCANT DRYER

108 MM Ø PIPE BRIDGE TABLET & WAREHOUSE

GOOD PRATICE CASE STUDY Compressed Air

CONCLUSION The energy audits at Carbery Milk Products and Wyeth Medica identified ways in which the operating costs of the compressed air systems could be significantly reduced and system performance improved. Most of the savings identified were in the areas of reducing losses and bottlenecks on the systems, together with improving compressor control. Although the recommendations made in these two case studies are site specific, they could be broadly applied to other compressed air systems. It was clear from both case studies that properly maintained compressors operate more efficiently. It was also clear that air consumption needs to be monitored and evaluated if it is to be properly controlled. Savings can be made by matching compressor loading as accurately as possible to air demand. Both studies illustrate the fact that significant savings can be achieved by implementing a programme to continuously monitor and repair leaks. The implementation of the type of changes proposed above would not only result in financial savings, it would also free up considerable amounts of generating capacity, allowing the site to expand further without the need for investment in new compressor capacity.

Air compressor at Wyeth Medica Ireland Ltd., Newbridge, Co. Kildare.

SYSTEM LEAKAGE Leaks can waste significant amounts of energy in an industrial compressed air system, sometimes up to 20 – 30% of a compressor’s output. While leaks can be found throughout the compressed air system, the most common problem areas are: » Couplings, hoses, tubes and fittings

A detailed site survey using ultrasonic leak detection equipment should highlight all system leaks. These can be categorised according to their severity on a scale of 1 to 10 with 10 being the worst. RATING

DESCRIPTION

» Pressure regulators

1

VERY SMALL – CAN ONLY BE IDENTIFIED USING ULTRASOUND

» Open condensate traps and shut-off valves

2

VERY SMALL – CAN BE HEARD

3

SMALL – CAN BE HEARD AND FELT

» Pipe joints, disconnects and thread sealants

A good leak prevention programme will include the following components: » identification, tagging and repair » verification and re-evaluation

4 – 10

These are responsible for the majority of air loss and are therefore costing the most. Leaks with a rating of 3 are small but noticeable and should be repaired after the major leaks. Leaks with a rating of 1 and 2 are negligible and normally would be ignored, however, they should be monitored to ensure they do not increase over time.

MEDIUM TO VERY LARGE

As a general guide, leaks with a rating over 3 should be repaired or reduced as soon as possible.

For further information on energy saving technologies and initiatives, contact: Irish Energy Centre, Glasnevin, Dublin 9, Ireland. Tel: 01.836 9080. Fax: 01.837 2848.

The Irish Energy Centre is funded by the Irish Government under the National Development Plan 2000 – 2006 and part financed by the European Union.

IRISH ENERGY CENTRE www.irish-energy.ie